The present invention relates to a semiconductor device in which a plurality of semiconductor elements have a SOI (Silicon On Insulator)-Si layer and a method of manufacturing the same. More particularly, the present invention relates to a structure of an element isolation film and a method of manufacturing the same.
In a conventionally-known semiconductor device, a CMOS element and a bipolar element are integrally formed on a SOI substrate (U.S. Pat. No. 5,212,397). The SOI substrate is constituted of a silicon semiconductor substrate (Si-sub) 1 and a buried oxide film (BOX) 2 formed thereon, as shown in FIG. 23. The buried oxide film 2 is formed by doping oxygen ions into the semiconductor substrate. The SOI substrate has a bipolar region 9 and a CMOS region 10. CMOS elements 7 and 8 are formed in the CMOS region 10, whereas a bipolar element is formed in the bipolar region 9. More specifically, the CMOS elements 7 and 8 are formed in a thin single crystalline silicon layer 3 formed on the buried oxide film (BOX) 2 within the CMOS region 10. The buried oxide film (BOX) 2 is deeply etched within the bipolar region 9. Within the etched region of the buried oxide film (BOX) 2, a thick single crystalline silicon layer 4 is formed by epitaxial deposition. A semiconductor element (bipolar element) is formed in the single crystalline layer 4. Although only a single bipolar element is shown in the figure, bipolar elements are separated by an element isolation silicon oxide film 6 formed in the element isolation region. On the other hand, the CMOS elements 7 and 8 are separated by an element isolation silicon oxide film 5 in the element isolation region. The element isolation film 6 of the bipolar region 9 is formed thicker than the element isolation film 5 of the CMOS region 10 and therefore the height of the film 6 from the surface of the substrate is larger than that of the film 5. To explain more specifically, the element isolation film 6 of the bipolar region 9 differs in thickness from the element isolation film 5 of the CMOS region 10, and therefore, their heights from the surface of the substrate differ.
A bipolar transistor has an emitter, base, collector, and collector extraction layer which are formed in the single crystalline silicon layer 4 of the bipolar region 9, and an emitter electrode, base electrode, and a collector electrode which are formed on the single crystalline silicon layer 4. A PMOS transistor of a CMOS transistor structure has a P+ source/drain region formed in the single crystalline silicon layer 3 of the CMOS region, a gate oxide film formed on the single crystalline silicon layer 3, and a gate electrode 7 formed on the gate oxide film. An NMOS transistor of the CMOS transistor structure has an N+ source/drain region formed in the single crystalline silicon layer 3 of the CMOS region, a gate oxide film formed on the single crystalline silicon layer 3, and a gate electrode 8 formed on the gate oxide film.
As described in the above, in the conventional semiconductor device, the element isolation film 6 of the bipolar region 9 is formed thicker than the element isolation film 5 of the CMOS region 10. Thus, the height of the element isolation film 6 from the surface of the substrate is larger than the element isolation film 5. In other words, since the thickness of the element isolation film 6 of the bipolar region differs in thickness from the element isolation film 5 of the CMOS region 10, their heights from the surface of the substrate differ from each other. This makes it difficult to process a wiring layer formed over the bipolar region 9 and the CMOS region 10. More specifically, in the manufacturing process of a semiconductor device having a plurality of SOI-Si layers different in thickness on a single SOI substrate, since element isolation is performed after a plurality of SOI-Si layers different in thickness are formed, the heights of the insulating films of the element isolation region differ. Therefore, it is difficult to process a wiring layer in a wiring formation step performed later. Furthermore, as a result of the insulating films of the element isolation region differing in height, xe2x80x9cout-of-focusxe2x80x9d occurs in a lithography step later performed, rendering it difficult to perform a micro gate processing.
There is another publication (U.S. Pat. No. 5,294,823) besides the aforementioned publication (U.S. Pat. No. 5,212,397) in which a plurality of single crystalline semiconductor layers different in thickness which are formed on a buried insulating film, are integrally formed into a single chip. However, in this conventional example, the element isolation regions of the bipolar region and the CMOS region 10 differ in height from the surface of a semiconductor substrate. Therefore, the same problems as in U.S. Pat. No. 5,212,397 resides also in U.S. Pat. No. 5,294,823.
The present invention has been made under the aforementioned problems. An object of the present invention is to provide a semiconductor device and a method of manufacturing the semiconductor device in which the insulating films of the element isolation region in a bipolar region have substantially the same height as that in the CMOS region, enabling micro wiring processing easier.
The present invention is directed to a semiconductor device having a plurality of semiconductor elements having a SOI-Si layer, which is characterized in that the element isolation films of a plurality of semiconductor elements have the substantially the same height from the surface of the semiconductor substrate, that is, the surfaces of the element isolation films form substantially the same plane. Furthermore, the present invention is characterized in that after element isolation regions are formed so as to form the same plane having the same height from the surface of the semiconductor substrate a plurality of SOI-Si films (single crystalline silicon film) different in thickness are formed.
According to the present invention, element isolation insulating films have substantially the same height from a semiconductor substrate. Therefore, wiring processing can be performed easier. Furthermore, according to the present invention, it is possible to manufacture a semiconductor device having a plurality of semiconductor elements having SOI-Si layers different in thickness without increasing the number of steps.
In a first aspect of the present invention, there is provided a semiconductor device comprising: a semiconductor substrate; a buried insulating film formed on the semiconductor substrate; a plurality of single crystalline semiconductor layers, each having a semiconductor element formed therein and being formed on the buried insulating film; and an element isolation region formed between adjacent single crystalline semiconductor layers, the element isolation insulating films formed in the element isolation region and having substantially the same height from the surface of the semiconductor substrate.
In the semiconductor device according to the first aspect of the present invention, at least one of the plurality of single crystalline semiconductor layers may differ in thickness from other single crystalline semiconductor layers. In the semiconductor device, the single crystalline semiconductor layers may include a first single crystalline semiconductor layer having a MOS transistor formed therein and a second single crystalline semiconductor layer having a bipolar transistor formed therein, the first and second single crystalline semiconductor layers having substantially the same film thickness and a thickness of the semiconductor layer lower than the gate electrode of the MOS transistor being lower than the film thickness of the second single crystalline semiconductor layer. In the semiconductor device, in the single crystalline semiconductor layers, a full depletion element and a partially Depletion element may be formed.
In the semiconductor device according to the first aspect of the present invention, the single crystalline semiconductor layers may include a first single crystalline semiconductor layer having a MOS transistor formed therein and a second single crystalline semiconductor layer having a bipolar transistor formed therein, the first and second single crystalline semiconductor layers having substantially the same film thickness and a thickness of the semiconductor layer lower than the gate electrode of the MOS transistor being lower than the film thickness of the second single crystalline semiconductor layer. In the semiconductor device, in the single crystalline semiconductor layers, a full depletion element and a partially Depletion element may be formed.
In the semiconductor device according to the first aspect of the present invention, in the single crystalline semiconductor layers, a full depletion element and a partially Depletion element may be formed.
In a second aspect of the present invention, there is provided a semiconductor device comprising: a semiconductor substrate having a first region and a second region; a buried insulating film formed in the first region of the semiconductor substrate; at least one first single crystalline semiconductor layer having a semiconductor element formed therein and formed in the buried insulating film and; at least one second single crystalline semiconductor layer formed in the second region and in contact with the semiconductor substrate; and an element isolation region for isolating the single crystalline semiconductor layers from each other, wherein all the element isolation insulating films in the element isolation region have the same height from the semiconductor substrate.
In the semiconductor device according to the second aspect of the present invention, the first single crystalline semiconductor layer formed in the first region may consist of a plurality of semiconductor layers having a plurality of film thicknesses. In the semiconductor device, a CMOS element may be formed in the first region and a bipolar element may be formed in the second region. In the semiconductor device, a MOS transistor may be formed in a predetermined first single crystalline semiconductor layer of the first region; a bipolar transistor may be formed in a predetermined second single crystalline semiconductor layer of the second region; the first and second single crystalline semiconductor layers have substantially the same height from the surface of the semiconductor substrate; and the thickness of the semiconductor layer lower than the gate electrode of the MOS transistor is substantially the same as the thickness of a predetermined second single crystalline semiconductor layer.
In the semiconductor device according to the second aspect of the present invention, a CMOS element may be formed in the first region and a bipolar element may be formed in the second region. In the semiconductor device, a MOS transistor may be formed in a predetermined first single crystalline semiconductor layer of the first region; a bipolar transistor may be formed in a predetermined second single crystalline semiconductor layer of the second region; the first and second single crystalline semiconductor layers have substantially the same height from the surface of the semiconductor substrate; and the thickness of the semiconductor layer lower than the gate electrode of the MOS transistor is substantially the same as the thickness of a predetermined second single crystalline semiconductor layer.
In the semiconductor device according to the second aspect of the present invention, a MOS transistor may formed in a predetermined first single crystalline semiconductor layer of the first region; a bipolar transistor may formed in a predetermined second single crystalline semiconductor layer of the second region; the first and second single crystalline semiconductor layers have substantially the same height from the surface of the semiconductor substrate; and the thickness of the semiconductor layer lower than the gate electrode of the MOS transistor is substantially the same as the thickness of a predetermined second single crystalline semiconductor layer.
In a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming a semiconductor substrate by laminating a buried insulating film, a single crystalline semiconductor layer, a first insulating film subsequently in this order; etching the first insulating film and the single crystalline semiconductor layer to form a plurality of laminate films consisting of the single crystalline semiconductor layer and the first insulating film in the buried insulating film; forming a second insulating film on the semiconductor substrate so as to cover the laminate films; flattening the second insulating film until the height of the second insulating film from the semiconductor substrate becomes the same as that of the first insulating film, thereby forming an element isolation region; etching away the first insulating film constituting at least one laminate film to expose a surface of the single crystalline semiconductor layer under the first insulating film; and depositing the single crystalline semiconductor to a predetermined depth on the exposed single crystalline semiconductor layer.
In a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming a semiconductor substrate by laminating a buried insulating film, a single crystalline semiconductor element, a first insulating film subsequently in this order; etching the first insulating film and the single crystalline semiconductor layer to form a plurality of laminate films consisting of the single crystalline semiconductor layer and the first insulating film on the buried insulating film; forming a second insulating film on the semiconductor substrate so as to cover the laminate films; flattening the second insulating film until the height of the second insulating film becomes substantially the same as that of the first insulating film to from an element isolation region; etching away at least one laminate film and simultaneously etching away the buried insulating film under the removed laminate film, thereby exposing a surface of the semiconductor substrate; etching the first insulating film constituting at least one laminate film excluding the removed laminate film, thereby exposing a surface of the single crystalline semiconductor layer under the first insulating film; and depositing a single crystalline semiconductor on the exposed single crystal semiconductor layer to thicken the single crystalline semiconductor layer, and simultaneously forming a single crystalline semiconductor layer on an exposed surface of the semiconductor substrate, thicker than the single crystalline semiconductor layer formed on the buried insulating film.
In a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming a semiconductor substrate by laminating a buried insulating film, a single crystalline semiconductor layer, a first insulating film subsequently in this order; etching the first insulating film and the single crystalline semiconductor layer to form a plurality of laminate films consisting of the single crystalline semiconductor layer and the first insulating film on the buried insulating film; forming a second insulating film on the semiconductor substrate so as to cover the laminate films; flattening the second insulating film until the height of the second insulating film from the semiconductor surface becomes substantially the same as that of the first insulating film to from an element isolation region; etching away the first insulating film constituting at least one laminate film to expose a surface of the single crystalline semiconductor layer under the first insulating film; forming a MOS transistor on the single crystalline semiconductor layer whose surface is exposed; etching away the first insulating film formed on a predetermined single crystalline semiconductor layer within the single crystalline semiconductor layer covered with the first insulating film; depositing a single crystalline semiconductor on the single crystalline semiconductor layer having the MOS transistor formed therein and on the single crystal semiconductor layer whose surface is exposed; and forming a bipolar transistor on a predetermined single crystalline semiconductor layer whose surface is exposed.
In a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming a semiconductor substrate by laminating a buried insulating film, a single crystalline semiconductor layer, and a first insulating film subsequently; etching the first insulating film and the single crystalline semiconductor layer to form a plurality of laminate films consisting of the single crystalline semiconductor layer and the first insulating film on the buried insulating film; forming a second insulating film on the semiconductor substrate so as to cover the laminate films; flattening the second insulating film until the height of the second insulating film from the semiconductor surface becomes substantially the same as that of the first insulating film to from an element isolation region; etching away at least one laminate film and simultaneously etching away the buried insulating film under the removed laminate film to expose a surface of the underlying semiconductor substrate; depositing the single crystalline semiconductor layer in contact with the surface of the exposed semiconductor substrate; etching away the first insulating film constituting at least one laminate film excluding the removed laminate film to expose a surface of the single crystalline semiconductor surface; forming a MOS transistor on the exposed single crystalline semiconductor layer; depositing a single crystalline semiconductor on the single crystalline semiconductor layer having the MOS transistor formed therein and simultaneously depositing on the single crystal semiconductor layer formed on the semiconductor substrate whose surface is exposed, thereby rendering the height of the single crystalline semiconductor layer having the MOS transistor therein, from the surface of the semiconductor substrate, substantially the same as that of the single crystalline semiconductor layer formed on the semiconductor substrate whose surface is exposed; and depositing the single crystalline semiconductor and forming a bipolar transistor on the single crystalline semiconductor layer formed on the semiconductor substrate whose surface is exposed.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.